Google Now, asssitente the Google voice is available on iOS (iPhone / ipad / ipod touch) that on Android devices, introduced a “Easter Egg”, that is a weird function that has nothing to do with the actual operation of the application: the possibility of sing some Christmas songs in Karaoke!The Christmas karaoke is available within Google Now (Google voice search).
Just open Google narrator and say "Let's go caroling”.
Don't worry if your English is not perfect and Google doesn't understand what you are asking.. instead of pronouncing voice, you can simply write, in the search box of Google Now on your iPhone or Android device “Let ’ go caroling” and you'll see a screen where you can choose which song to sing:
The ’ interface is nice, and a ball that bounces (Walt Disney style) will show you the text to sing karaoke!!
Have fun, and happy holidays to all !